Average inbreeding levels in US Holsteins is accelerating and should send alarm bells to producers using bulls on a random basis, warns a University geneticist.

This means a “new dawn” for “Genomic Future Inbreeding”, a predictive tool assigned to bulls expressed as a percentage.

This is according to Dr Les Hansen, University of Missouri, who has drawn attention to a “noteworthy” jump in average Holstein inbreeding of 0.4 per cent in two years.

His message is that good, accurate pedigree records on Holstein farms are vital to match appropriate heifers with bulls and that the days of randomly inseminating are over.

Average inbreeding has increased from 4.7 per cent in 2001 to 6.5 per cent in 2015, a point reached by Ayrshires in 2013.

Historically, geneticists have used 6.25 per cent as a guideline, explained Dr Hansen.

Dr Hansen said: “Dairy producers in the US typically breed their Holstein heifers and cows with semen from Holstein A.I. bulls on a random basis without regard to pedigrees and the potential for inbreeding.

He also stressed the importance of using computerised mating programs to assign semen from A.I. bulls individually to heifers and cows.

A greater awareness of inbreeding exists in non-Holstein breeds due to Jersey, Guernsey, Brown Swiss and Ayrshire populations being smaller.

For this reason, Dr Hansen says current Jersey and Guernsey inbreeding levels, of 7.5 and 7.4 per cent, are of greater concern than levels seen in the larger Holstein herd.

However, he said the jump in average Holstein inbreeding should “catch the attention” of producers and the wider industry.

He added: “Mounting concern about the effects of inbreeding within the pure breeds has led some dairy producers to turn to crossbreeding systems.

“For those producers who want to maintain pure Holstein cows, the crossing of inbred lines of Holsteins in rotation via the StrataGEN™ programme of Select Sires, Inc. provides an opportunity to avoid inbreeding depression for commercial milk production while maintaining a pure Holstein herd.”